I also carry a compressor, in my case a nice little Fini AirBoss. (Sears also sells the same compressor under their name.) This is about the most compact "real" 120V compressor I could find for a somewhat reasonable price, and it works a treat.
If you just need a little air to top up a tire, perhaps because you've gone from a warm climate to a cold one, a good bicycle tire pump is also an option...maybe not a particularly fast or fun one, but most likely quicker than the cheap little 12V compressor/inflator gizmos and assuredly a whole lot quieter. I don't think I would care to inflate a completely flat motorhome tire with one, however.